Electrolytic bismuth/carbon nanotubes composites for high-performance sodium-ion battery anodes

Abstract Bismuth (Bi) is an attractive anode for sodium-ion batteries (SIBs) because of its unique structure, large lattice spacing along c-axis (d(003) = 3.95 A), and high volumetric capacity (3800 mAh·cm−3). However, like other alloy-type anodes (such as Antimony (Sb), Tin (Sn), Germanium (Ge)), the pulverization of Bi due to severe volume expansion (≈250%) after sodiation results in instability and degradation of solid electrolyte interphase (SEI) as well as rapid capacity fade. Here, a Bismuth/Carbon Nanotubes (Bi/CNTs) composite anode is prepared by one-step electro-deoxidation to address such issues. The electrolytic micro-Bi/CNTs composite relieves the effect of volume expansion and thereby improves its cycling performance. The capacity of Bi/CNTs is 381.6 mAh·g−1 at 2.0 A·g−1 with a capacity retention of 99.5% after 1000 cycles, which corresponds to a capacity fade of 0.0005% per cycle. Therefore, this paper shows a green approach to prepare Bi/CNTs composite anode with advantages of the low-cost bismuth trioxide (Bi2O3) feedstocks as well as the synergetic effect between electrolytic Bi and CNTs.